When data and/or control messages are communicated between transmitting and receiving devices in a communication system over a wireless interface, typically some type of error detection and error correction mechanism is used to assist in the decoding of the message at the receiving device to enable further processing. Generally, messages are transmitted as a series of data units, each having a predetermined logical structure and having a plurality of different types of fields for organizing bits in the data unit. One or more or these fields typically contain bits that enable error detection and/or error correction for that field. However, depending on the protocol used, some fields may include error correction bits but not error detection bits or limited error detection bits because of a bit number constraint due to, for instance, bandwidth constraints associated with the physical channels over which the data unit is sent. A resulting limitation is an inability to detect decoding errors in some fields can cause problems related to the further processing of the data unit if there are, in fact, errors that go undetected.
An example of an air interface protocol that has a data unit structure that includes fields having error correction but not error detection is the air interface protocol defined in accordance with the European Telecommunications Standards Institute (ETSI) Technical Specification (TS) 102 361 (hereinafter referred to as “ETSI specification”). A data unit structure identified in this technical specification is a burst, which is defined as the smallest predefined group of continuous bits containing information or signaling. More particularly, described therein is a digital mobile radio (DMR) time division multiple access (TDMA) burst. The DMR TDMA burst includes, for instance, a data type field that identifies the type of data being transmitted in an information field, which is also included in the burst. There are a number of data types mentioned in the technical specification including, e.g., voice link control (LC) header, terminator with LC, control signaling block (CSBK), data header, multi-block control (MBC) header, MBC continuation, rate ½ data continuation, rate ¾ data continuation, etc. Since the data type field is subject to error correction (in this case forward error correction (FEC) which is well known in the art) but not error detection, it may not be possible for a receiver to know whether the error correction on the data type field was successful. Because of this, it may be possible under certain error conditions for some burst types to be identified and/or processed incorrectly. In the case of a multi-burst message, this may result in either the entire message failing and being discarded (for an unconfirmed message) or automatic repeat requests (ARQ) that need to be transacted on the channel (for a confirmed message). Either result is undesirable as the former results in a failed communication attempt while the latter consumes additional bandwidth to manage the repeat requests.
Accordingly, there is a need for a system and method for reliably receiving and processing multi-burst messages even if the data type field for one or more of the bursts in the multi-burst message is not processed correctly.
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